All of the bags, some of which proclaimed they were "pre-washed" or even "triple-washed," were analyzed before their sell-buy date.

The tests by Consumer Reportsrevealed that nearly 40 percent of the samples contained levels of bacteria that exceed industry experts' recommendations for healthy consumption. While results varied by state and even by brand, many of the contaminated packages sold spinach and were analyzed within a week of their sell-buy date.

It didn't matter what kind of bag the greens came in -- or if they were organic.

So what can you do? If you buy salad greens in the store, opt for the packages that are at least six to eight days away from their use-by date. Consumer Reports found those items had lower levels of bacteria.

Also, wash your greens yourself! Just because the bags say the produce has been washed, or even washed multiple times, it's beneficial to re-wash the greens before you eat them. Rinsing the greens won't get rid of all the bacteria, but it will eliminate little dregs of soil clinging to your food. The Consumers Union also recommends you keep your greens away from raw meat to prevent any pathogenic cross-contamination.

Consumer Reports conducted the tests at an external lab over a period of two weeks with help from the Pew Health Group, which works to improve the safety of your grub.